Training and nutrition for women: what female biology demands

Almost everything you have been told about training and nutrition has been based on data collected from men. That is not a matter of opinion—it is the historical record of exercise science. Exercise physiologist and nutrition scientist Dr. Stacy Sims has spent her career correcting this gap. Her central argument: women are not small men, and treating them as such comes at a real cost to their health and performance.

Why the research gap matters

For decades, women were excluded from exercise and nutrition research because hormonal variability made them harder to study. The result is that recommendations developed from male subjects—for training intensity, protein intake, recovery, fasting protocols—have been applied to women as though biological sex were irrelevant. It is not.

Women's physiology changes dramatically across life stages. The hormonal landscape of a 25-year-old is entirely different from that of a 42-year-old in perimenopause. Applying the same training prescription to both ignores a fundamental shift in how the body responds to stress, fuel, and recovery.

What changes in the 30s and 40s

In the early 30s, most women feel reasonably stable. The first signals of change typically emerge in the mid-30s: familiar training approaches stop producing the same results, body composition becomes harder to manage, and energy levels feel less predictable.

The 40s bring a more definitive shift. Estrogen and progesterone begin fluctuating rather than following reliable cycles. Progesterone, which has protective effects on the brain and the gut, starts declining. The gut microbiome itself shifts in response to these hormonal changes, with a rise in the types of bacteria that promote fat storage, increase appetite for simple carbohydrates, and impair insulin sensitivity. These changes interact with each other in ways that can feel overwhelming—and they are often attributed to willpower or stress rather than physiology.

Understanding that these changes are biological—and therefore addressable with the right inputs—is the starting point.

What actually works: training

High-intensity interval training

High-intensity work is one of the most important tools for women, particularly from the late 30s onward. The reason is mechanistic: intense effort triggers GLUT4 proteins in muscle tissue to translocate to the cell surface, allowing glucose to enter muscle cells independently of insulin. This improves insulin sensitivity in a durable, structural way and helps counteract the metabolic shifts that come with perimenopause.

High intensity means genuinely hard effort—an all-out sprint lasting 20 to 30 seconds followed by two to three minutes of full recovery. The recovery period is not optional; without it, the next effort cannot reach true high intensity, and the training stimulus is lost. Four to five sprints per session, no more than two to three times per week.

Lactate produced during high-intensity work is also a preferred fuel for the brain and heart. Regular exposure to elevated lactate trains the brain to use it efficiently, which is directly relevant to reducing the risk factors for amyloid and tau plaques associated with Alzheimer's disease.

Resistance training with heavy loads

Lifting heavy weights is protective for the brain in a way that moderate-intensity exercise is not. A large randomized controlled trial found that it was specifically the heavy-load resistance training—not moderate weight or high-rep training—that stimulated connectivity improvements in the prefrontal cortex, the region most associated with cognition and most vulnerable to Alzheimer's.

For bone health, the relevant stimulus is ground reactive force—landing hard enough that the force travels through the entire skeleton. Walking is not sufficient. Jump training and heavy compound lifts are.

It is never too late to start. Research on adults in their 70s and 80s consistently shows that heavier relative loads improve lean mass, bone density, and brain health markers. Begin with bodyweight movement, progress systematically, and aim over one to three years to work toward genuinely heavy loads relative to your capacity.

What actually works: nutrition

Protein—much more than the standard recommendation

The current recommended daily allowance for protein is a floor for preventing malnutrition, not a target for health. For women focused on maintaining muscle mass and bone density, the research supports 1.6 to 2 grams of protein per kilogram of body weight daily—roughly 0.8 to 1 gram per pound. At 150 pounds, that is 120 to 150 grams per day.

As women age, they become increasingly anabolically resistant: the body requires a stronger stimulus—more protein and more intense resistance training—to maintain the same amount of muscle. This makes adequate protein intake progressively more important, not less.

Post-exercise protein timing also becomes more significant with age. The older the body, the more important it becomes to consume protein in the window immediately following training.

Caution with fasting protocols

Intermittent fasting protocols developed and studied primarily in men do not translate automatically to women, particularly for women in their reproductive years or in perimenopause. Extended fasting can dysregulate cortisol in women in ways that worsen hormonal balance rather than improving it. Women who are drawn to fasting approaches should approach them conservatively and monitor how they feel, particularly regarding energy, mood, and cycle regularity.

The longevity perspective

Strength and high-intensity work compound over time. Fitness does not have to decline on a fixed trajectory. What you do now—particularly resistance training and high-intensity cardio—builds a structural foundation in muscle, bone, and brain that will determine your capacity in your 60s, 70s, and beyond.

The first practical step is straightforward: schedule time for training as a non-negotiable meeting with yourself. Block it in the calendar the same way you would a work appointment. That shift in priority is where everything else follows.